1. Technical Field
This invention relates generally to a seal, and more particularly to a seal suitable for use in situations involving vibration and water vapor.
2. Description of the Related Art
There are, in principle, two types of seals. The first type is called a radial seal, and prevents convective flow perpendicular to the central axis of the hole. A circular disc between two flanges is an example of a radial seal. The second type is called an axial seal, and prevents convective flow parallel to the axis of the hole. An o-ring around a shaft and a cork in a hole are examples of an axial seal.
When designing a seal, there are several factors to consider. One consideration is diffusive mass flow, the other is convective mass flow. Diffusion is caused by a concentration gradient, whereas convection is caused by a pressure gradient. Most conventional seals that deal with diffusion and convection mass flow do not, however, work well in mechanically variable conditions or where the environment has a great deal of water and humidity. Generally, the diffusion of water vapor past a seal cannot be completely stopped, but is rather controlled by the seal design.
Ideally, a seal for use in an automobile should be capable of being fully submerged without permitting any detrimental effect on the product protected by the seal. The seal should also be capable of operating in a dynamic environment, such as where there is sustained vibration. Moreover, to be cost effective, the application surface is often not very smooth, and the seal design should therefore be relatively insensitive to the roughness of the application surface.